In the related art, a working machine with a motor generator for assisting an engine includes a storage battery, such as a capacitor, for supplying electric power to the motor generator and charging regenerative power. Since such a capacitor is used in an environment where charging and discharging are repeatedly performed, various studies for increasing the life of the capacitor are in progress.
For example, taking into consideration that a capacitor deteriorates if the voltage value of the capacitor is increased too much, it is proposed that a discharge setting value is set for the voltage value of the capacitor and discharging is performed to lower the voltage value of the capacitor to the discharge setting value or lower if the charge voltage of the capacitor exceeds the discharge setting value when the working machine stops working, so that the life of the capacitor can be increased. Discharged electric power is stored in an auxiliary battery (for example, see Patent Document 1).